mapstructure

mapstructure is a Go library for decoding generic map values to structures and vice versa, while providing helpful error handling.

This library is most useful when decoding values from some data stream (JSON, Gob, etc.) where you don't quite know the structure of the underlying data until you read a part of it. You can therefore read a map[string]interface{} and use this library to decode it into the proper underlying native Go structure.

Installation

go get github.com/go-viper/mapstructure/v2

Migrating from github.com/mitchellh/mapstructure

@mitchehllh announced his intent to archive some of his unmaintained projects (see here and here). This is a repository achieved the "blessed fork" status.

You can migrate to this package by changing your import paths in your Go files to github.com/go-viper/mapstructure/v2. The API is the same, so you don't need to change anything else.

Here is a script that can help you with the migration:

sed -i 's/github.com\/mitchellh\/mapstructure/github.com\/go-viper\/mapstructure\/v2/g' $(find . -type f -name '*.go')

If you need more time to migrate your code, that is absolutely fine.

Some of the latest fixes are backported to the v1 release branch of this package, so you can use the Go modules replace feature until you are ready to migrate:

replace github.com/mitchellh/mapstructure => github.com/go-viper/mapstructure v1.6.0

Usage & Example

For usage and examples see the documentation.

The Decode function has examples associated with it there.

But Why?!

Go offers fantastic standard libraries for decoding formats such as JSON. The standard method is to have a struct pre-created, and populate that struct from the bytes of the encoded format. This is great, but the problem is if you have configuration or an encoding that changes slightly depending on specific fields. For example, consider this JSON:

{
  "type": "person",
  "name": "Mitchell"
}

Perhaps we can't populate a specific structure without first reading the "type" field from the JSON. We could always do two passes over the decoding of the JSON (reading the "type" first, and the rest later). However, it is much simpler to just decode this into a map[string]interface{} structure, read the "type" key, then use something like this library to decode it into the proper structure.

Credits

Mapstructure was originally created by @mitchellh. This is a maintained fork of the original library.

Read more about the reasons for the fork here.

License

The project is licensed under the MIT License.